1. Field of the Invention
The present invention concerns the area of projection display systems and, more specifically, a compact desktop display that provides a large image and enables eye contact while video teleconferencing.
2. Description of Related Art
The information age has transformed and is transforming the very nature of society, including how work is done and the way humans relate to each other. Fiber optic and satellite data transmission, new data compression methods, high speed modems, and powerful personal computers are all accelerating this transformation. This new information age is fundamentally linked to the increasing use of various display technologies for viewing the digital world on television and computer screens.
The ergonomics of desktop computing has been an important consideration in the design of personal computers and computer work stations for some time. In spite of this, there remains at least one significant obstacle to overcome. That obstacle stems from the computer user's demand for larger and larger displays for the desktop, while current display technology is unable to provide an ergonomically sound solution to this demand. Current displays are excessively bulky to be conveniently placed on a desktop. A 35-inch diagonal CRT (cathode ray tube) monitor occupies the entire desk, as do rear projection devices with similar viewing areas. These bulky displays render installations ergonomically unsound because the viewing surface of the screens are placed mere inches away from the user. The close proximity of these large displays makes viewing of the entire display at a single glance impossible and causes severe neck and eye strain because of the physical movement required to scan the entire display.
Flat panel displays offer the potential for a far superior large display for desktop computing because the flat panel display can be positioned to the rear of the desk away from the user, thus allowing the user to both enjoy the entire large picture in a single glance without the physical strain of extreme neck and eye movements. Despite the promise of large flat panel display technology, their consumer availability remains uncertain. This is particularly the case with large flat panel displays of 35 inches diagonally and greater. The technologies currently proposed by electronics manufacturers suffer from the problems of low brightness, poor resolution, limited viewing angle, and poor contrast, to name only a few. Even with these problems resolved, the high projected price for large flat panels may well prove prohibitive for most consumers.
With the merging of television and computer, the demand for larger displays will only increase. A larger display for the desktop naturally provides more involving CD-ROM game experiences, easier to view windows while multitasking and greater detail in graphics and diagrams. Beyond these immediate advantages, a large desktop computer display could also provide ideal ergonomics for quality video-conferencing. Studies have shown that conferees feel much more engaged in the conference when the image of the distant party is life size. Unfortunately, as video-conferencing improves due to a larger display, the ergonomics of eye contact between conferees is made worse by the larger display.
A fundamental problem with all video-conferencing is the lack of eye contact between conferees. This problem, known as the parallax problem, is caused by a camera being placed at the perimeter of the display so as to not obstruct the viewing of the display. In this arrangement a local conferee looks into the display to view the distant conferee, but when he does so he fails to look directly into the camera. Hence, a camera placed above the display causes the conferee to appear to be looking down. This problem is so exacerbated by large displays where the distance between the camera and the center of the display is maximized that the video conference seems extremely awkward and unnatural.
Numerous eye contact technologies have been proposed. U.S. Pat. No. 5,278,681 to Gitlin teaches the use of a flat panel liquid crystal projection screen with a camera mounted behind the viewing surface. This technology relies on projectors resulting in a bulky housing due to the required "throw" distance of the projector. Also, it seems unlikely that such a display could ever be configured into large panels. The most common approach to solve the eye contact problem is to use a transparent-reflective panel, i.e., a beamsplitter, positioned at a 45-degree angle relative to the viewing surface of the display. The camera in this arrangement is placed at right angles to the display and is aimed toward the transparent-reflective panel to capture the reflection of the conferee as he peers through the transparent-reflective panel to the display beyond. Although quality eye contact can be achieved when this system is used with a large display on a desktop, the transparent-reflective panel extends far beyond the edge of desk into the space normally occupied by the conferee.
Prior Art Desktop Displays
Prior art FIG. 1 demonstrates the poor ergonomics of a conventional rear projection screen placed on a desktop. A rear projection screen 6 is positioned toward the front edge of a desk 2. As a result an observer seated at the desk is forced to strain to view a large image produce on the rear projection screen 6. Typically in rear projection housings a mirror 8 is used to "fold" the optical path to shorten the apparent focal distance of a projector 8.
Likewise, prior art FIG. 2 demonstrates that a CRT display 10 on the desk 2 also suffers from poor ergonomics. Most desktop computer systems use CRT monitors ranging from about 12 to about 20 inches diagonal. Even at 20 inches, diagonal CRT displays begin to suffer from having the display screen too close to the position of the seated observer. The CRT display 10 is shown in FIG. 2 with its viewing surface near the front edge of the desk. In such an arrangement a computer operator cannot view the entire picture at a single glance, and eye strain and neck strain result because of the extreme movements necessary to scan the entire viewing surface. For larger displays, such as 35 inches diagonal, the bulky CRT display 10 can even extend over the edge of the desk 2 almost into the lap of the observer.
Prior art FIG. 3 illustrates a flat panel display 12 on the desk 2. The flat panel display 12 can be positioned toward the rear of the desk. At the rear of the desk a 35-inch diagonal image is sufficiently far from the observer seated at the desk to allow the observer to take in the entire image in single glance and scan the image without a fatiguing amount of eye and neck movement. Although the observer-to-image distance is ideal when the flat panel display 12 is used, several problems remain in the way of practical flat panel display 12 use. The first and most apparent problem is that flat panel technology has yet to mature to high quality large images similar to those of the cathode ray tube. This leads to another problem with large flat panel display technology; that is, the ongoing technical development may take many years before such displays are available to the consumer. Still, another problem, if and when large flat panels are available for consumers' purchase, their price is likely to be far too high for the vast majority of consumers to afford. Lastly, a primary thrust in the near future for large desktop displays will be video teleconferencing. All the flat panel technologies now in development, as far as the inventors know, do not permit eye contact between conferees without major technological modifications. The use of a transparent-reflective panel angled in front of the flat panel display 12 at 45 degrees with a camera capturing the reflection of the conferee will provide quality eye contact. Unfortunately, the flat advantage of the flat panel display 12 is diminished by the increased depth of the display due to the desk space taken up by the angled transparent-reflective panel.